.\" Copyright (c) 1983 Regents of the University of California.
.\" All rights reserved.  The Berkeley software License Agreement
.\" specifies the terms and conditions for redistribution.
.\"
.\"	@(#)dmc.4	6.3.1 (2.11BSD) 1996/10/22
.\"
.TH DMC 4 "October 22, 1996"
.UC 2
.SH NAME
dmc \- DEC DMC-11/DMR-11 point-to-point communications device
.SH SYNOPSIS
.ft B
.nf
/sys/conf/SYSTEM:
	NDMC	\fIdmc_controllers\fP	# DMC11
.fi
.ft R
.SH DESCRIPTION
The
.I dmc
interface provides access to a point-to-point communications
device which runs at either 1 Mb/s or 56 Kb/s.  DMC-11's communicate
using the DEC DDCMP link layer protocol.
.PP
The
.I dmc
interface driver also supports a DEC DMR-11 providing point-to-point
communication running at data rates from 2.4 Kb/s to 1 Mb/s.
DMR-11's are a more recent design and thus are preferred over DMC-11's.
The NXMT and NRCV constants in the driver should be increased in this case,
as the DMR can accept up to 64 transmit and receive buffers, as opposed
to 7 for the DMC.
.PP
The configuration flags specify how to set up the device, 
.br
0 -- full duplex DDCMP (normal mode)
.br
1 -- DDCMP Maintence mode (generally useless)
.br
2 -- DDCMP Half Duplex, primary station
.br
3 -- DDCMP Half Duplex, secondary station
.ti
.PP
Several device error counters are available via "adb", for
more information see the adb script /usr/share/adb/dmcstats, or the
DMC11 technical manual.
.PP
The host's address must be specified with an SIOCSIFADDR ioctl,
and the destination address specified with a SIOCSIFDSTADDR ioctl,
before the interface will transmit or receive any packets.
.SH ROUTING
The driver places a HOST entry in the kernel routing tables for the
address given in the SIOCSIFDSTADDR ioctl.  To use the DMC as a
link between local nets, the route to the remote net must be added manually
with the
.IR route (8)
command, or by the use of the routing process
.IR routed (8)
on each end of the link.
.SH DIAGNOSTICS
.BR "dmc%d: bad control %o" .
A bad parameter was passed to the
.I dmcload
routine.
.PP
.BR "dmc%d: unknown address type %d" .
An input packet was received which contained a type of
address unknown to the driver.
.PP
.BR "DMC fatal error 0%o" .
A fatal error in DDMCP occurred, causing the device to be restarted.
.PP
.BR "DMC soft error 0%o" .
A non-fatal error in DDMCP has occurred. 
.PP
.BR "dmc%d: af%d not supported" . 
The interface was handed a message which has
addresses formatted in an unsuitable address family.
.SH SEE ALSO
intro(4N), inet(4F)
.SH BUGS
The current version of the driver uses a link-level encapsulation
so that multiple protocol types may be used.
It is thus incompatible with earlier drivers,
including the 4.2BSD version.
